Quantitative X-ray computer assisted tomography (CT) analyses in healthy aging men and women demonstrated significant sex differences in lateral ventricular volume and in age of onset of lateral ventricular enlargement. Longitudinal analysis of serial CT scans showed that the rate of ventricular dilation prior to the onset on nonmemory cognitive deficits in patients with dementia of the Alzheimer type (DAT) is less than after the onset of these deficits. Age-related subcortical gray matter atrophy, ventricular dilatation, and the expansion of peripheral cerebrospinal fluid (CSF) volume was found in healthy men using magnetic resonance imaging (MRI). MRI showed a significant age-related decrease of posterior frontal, but not of temporal lobe volume in healthy men. Men with mild DAT had significantly less brain matter than did healthy age-matched controls. Mean volumes of both the right and left lateral ventricles were significantly larger in the neurologically and cognitively normal hypertensives as compared to controls using MRI. Whereas enlargement of the lateral ventricles appears to be a concomitant of normal aging, our findings suggest that longstanding hypertension results in greater ventricular enlargement than would be expected on the basis of age alone. 31P spectra, and fluorodeoxyglucose positron emission tomographic (PET) scans were obtained from DAT patients and healthy age-matched controls. Phosphorus metabolite concentrations or ratios did not differ between patients and controls. Glucose metabolic rates in the same volume of brain were significantly reduced in DAT patients relative to controls. These results suggest that disturbances in cellular phosphate energy reserves and membrane phosphoester metabolite levels do not play a major role in the neuropathology of DAT, at least in bulk regions of the brain.